Bearing cage with depressed slot end

ABSTRACT

A flat strip of metal is formed to provide a depressed center relief portion between two edge portions. Depressions are formed in the two edge portions and center slots are pierced across the center relief portion such that roller receiving slots are formed with slot end depressions at both ends of the roller receiving slots. The partially formed bearing cage is then formed into a circular hoop such that the edge portions form rings at the axial ends of the circular hoop. The resulting roller bearing cage of the present invention may also be formed by other methods.

BACKGROUND OF THE INVENTION

This invention relates generally to roller bearing cages and, moreparticularly, to roller bearing cages of "sigma" configuration.

Roller bearings commonly employ separators, retainers or cages tomaintain separation and alignment of the rollers. Although the terms arefrequently used interchangeably, the term "cage" is often used todescribe a device that retains the rollers both radially and axially.Thus, a roller bearing cage prevents rollers from moving axially orradially out of the cage, allowing the cage and rollers to be handled asa bearing subassembly.

One particular type of roller bearing cage is known as a sigma cage. Asillustrated in FIG. 1, a typical sigma cage 10 has annular end rims 12and 14, axially spaced apart along a common axis, joined together bycrossbars 16 to form slots 18 for receiving rollers, not shown.Crossbars 16 have a central portion 20 offset radially inwardly fromlaterally outward portions 22 and 24 such that, when viewed inlongitudinal section, end rims 12 and 14 and crossbars 16 resemble theGreek letter "sigma".

End rims 12 and 14 extend radially as end flanges 26 and 28,respectively. End flanges 26 and 28 provide stop surfaces which assistslots 18 to ensure that axial movement of the rollers is restricted.Edge surfaces on central portion 20 prevent radially inward movement ofthe rollers and edge surfaces of laterally outward portions 22 and 24prevent radially outward movement of the rollers.

In some applications, a significant axial offset is required between theroller pockets (slots) and the end flanges of the cage. Such offsetmaterially affects the axial containment of the rollers because the endflanges no longer provide stop surfaces proximate to the slots. As aresult, roller loss can occur during handling of the cage beforeinstallation or upon installation of the bearing in the housing.

The foregoing illustrates limitations known to exist in present rollerbearing cages of sigma configuration. Thus, it is apparent that it wouldbe advantageous to provide an alternative directed to overcoming one ormore of the limitations set forth above. Accordingly, a suitablealternative is provided including features more fully disclosedhereinafter.

SUMMARY OF THE INVENTION

In one aspect of the present invention, this is accomplished byproviding a method for forming a roller bearing cage with depressed slotends. A flat strip of metal is formed to provide a depressed centerrelief portion between two edge portions. Depressions are formed in thetwo edge portions and center slots are pierced across the center reliefportion such that roller receiving slots are formed with slot enddepressions at both ends of the roller receiving slots. The partiallyformed bearing cage is then formed into a circular hoop such that theedge portions form rings at the axial ends of the circular hoop.

In another aspect of the present invention, a roller bearing cage isprovided having axially spaced end rims. Crossbars join the end rimssuch that roller receiving slots are formed, the crossbars having acentral portion radially offset with respect to laterally outwardportions such that a roller is retained in the radial directions.Radially offset rim portions are located between the crossbars such thata roller within one of the roller receiving slots is retained in eachaxial direction by engagement with one radially offset rim portion ateach end of the roller receiving slot.

The foregoing and other aspects will become apparent from the followingdetailed description of the invention when considered in conjunctionwith the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is an isometric view illustrating a prior art roller bearingsigma cage;

FIG. 2 is an isometric view illustrating an embodiment of the rollerbearing cage of the present invention;

FIG. 3 is a sectional view of two roller bearing cages of FIG. 2 asinstalled in an elongated bearing housing having a cross drilledlubrication hole; and

FIG. 4 is a diagram illustrating outlines of multiple punches that maybe used to pierce slots of the bearing cage of FIG. 2; and

FIG. 5 is a sectional view of a roller bearing cage illustrating asecond embodiment of the present invention.

DETAILED DESCRIPTION

Referring now to the drawings, FIG. 2 illustrates a preferred embodimentof roller bearing cage 30 of the present invention having annular endrims 32 and 34, axially spaced apart along a common axis, joinedtogether by crossbars 36 to form slots 38 for receiving rollers, notshown. Crossbars 36 have a central portion 40 offset radially inwardlyfrom laterally outward portions 42 and 44. Cage 30 is considered a sigmacage because end rims 32 and 34 and crossbars 36 suggest the Greekletter "sigma" when the cage is viewed in longitudinal section.

Unlike the roller bearing cage of FIG. 1, roller bearing cage 30 hasdepressed slot ends designed to abut end surfaces of bearing rollersreceived within slots 38. Abutment surfaces 46 are formed by periodicdepressions 48, one at each end of roller receiving slots 38, to preventescape of the bearing rollers, especially in the absence of closeproximity bearing cage flanges. Specifically, axial movement of thebearing rollers in both axial directions is limited by engagement ofabutment surfaces 46 by the bearing rollers.

In the particular embodiment shown, abutment surfaces 46 have a curvedprofile, curved with a circular arc or otherwise, along a transversesection of bearing cage 30. Depressions 48 are dimple-like recesseshaving a substantially angular longitudinal section and a substantiallyconical configuration. However, depressions 48 may be of various shape,depending on the shape of tooling used to form the recesses, asdescribed below.

End rims 32 and 34 comprise axially extending portions side 50 andflange portions 52 extending radially inwardly at the axially outwardends of axially extending side portions 50. Depressions 48 are formedwithin axially extending side portions 50 at locations between crossbars36. Abutment surfaces 46 are radially offset rim portions forming endsof slots 38. End rims 32 and 34 and crossbars 36 are formed from asingle sheet of steel or other metal and have substantially the samethickness.

As illustrated in FIG. 2, central portions 40 of crossbars 36 andabutment surfaces 46 are offset radially inwardly relative to laterallyoutward portions 42 and 44 of crossbars 36. However, the presentinvention is not limited to that configuration and may also be utilizedto provide an inverted sigma bearing cage, illustrated in FIG. 5, inwhich central portions 76 and abutment portions 78 are offset radiallyoutwardly. Similarly, flange portions 80 may extend radially outwardlyrather than radially inwardly or may be omitted.

FIG. 3 illustrates an example requiring a significant offset of theroller receiving slots from the bearing flanges. Two roller bearingcages 30, shown in longitudinal section, are installed in an elongatedbearing housing 54 having a cross drilled lubrication hole 56.Depressions 48 of end rims 32 and 34 allow two roller cage bearings tomaintain proper axial location of rollers 58 and 60 without rollerinterference to the breakout location of lubrication hole 56 on loadbearing shaft 62.

End washers 64 and 66 mounted on bearing housing 54 engage outwardflanges of roller bearing cages 30 to limit outward axial movement ofthe cages. Inward flanges of roller bearing cages 30 overlie lubricationhole 56 and abut each other to limit inward axial movement of the cages.Central portions 40 of crossbars 36 separate rollers 58 and 60circumferentially and cooperate with outward portions 42 (FIG. 2) tocontain the rollers during handling and installation.

The preferred method of manufacturing roller bearing cage 30 is by flatblank, wrap, and weld, using multislide techniques. Flat coil stock ofuniform section is pressed to form a depressed center relief portionbetween two edge portions. Pairs of slot end relief openings are piercedin the edge portions, and forming punches are seated against thelaterally outward edges of the slot end relief openings, thereby formingangled slot end depressions 48.

Center slots are then pierced across the center relief portion andbetween each pair of slot end relief openings to provide the remainingperimeter of slots 38 such that depressions 48 are at the ends of slots38. Strip edge gutting and flange forming may be used to trim and shapeedges of the resulting cage blank. The cage blank is cut to apredetermined length by a block cut from the formed strip. The completedblank is wrapped to a 360 degree circular hoop and welded such that theedge portions form rings at the axial ends of the resulting cage.

FIG. 4 illustrates outlines and relative positions of multiple punchesthat may be used to pierce slots 38 according to the method justdescribed. Heavier outlines 68 and 70 represent the shape of one pair ofslot end relief openings pierced in the edge portions of the flat strip.Light outline 72 represents the shape of tooling used to pierce thecenter slots across the slot end relief openings.

As shown by the positions illustrated, the opening pierced by the centerslot punch blends with the slot end relief openings, even if a slightmisalignment of the punches occurs. The separate cutting of the slot endrelief openings avoids distortion to the slot that might occur duringpressing to form depressions 48. Overlapping of the punches results incircumferentially extending trapezoidal shaped tabs 74 (also in FIG. 2)which extend into the roller receiving slots and assist in controllingradially outward movement of the rollers.

Alternatively, depressions 48 may be formed by pressing a "dimple" orrecess in the edge portions of the metal strip without piercing of slotend relief openings. The full perimeter of slots 38 would then bepierced such that a portion of the dimple remains, thereby providingdepressions 48. That method ensures a square profile (in longitudinalsection) abutment surface 46 which gives maximum contact with the endsof the rollers; however, tool maintenance with that alternative methodmay be more difficult.

Other variations in the method of manufacturing cage 30 or the invertedsigma bearing cage are included in the present invention. Depressions 48may be formed either before or after piercing of the center slots.Depressions 48 and slots 38 may also be formed and piercedsimultaneously or may be accomplished by a single tool. Strip edgegutting, flanging and welding steps may be added or omitted, as desired.Joining ends of the circular hoop may be by other means than welding ormay be omitted.

From the above description, it will be apparent that the presentinvention provides a solution to the end containment problem inconventional sigma bearing cages which results in roller loss duringhandling and upon bearing installation, especially when a significantoffset is required between the rollers and the end flanges. Axialemergence of the bearing rollers is prevented by roller contact with thedepressed slot end to maintain proper location of the rollers.

Having described the invention, what is claimed is:
 1. A roller bearingcage comprising:first and second end rims axially spaced apart withrespect to a common axis, each of the end rims having an axially outwardend, an axially extending side portion, and a plurality of periodicdepressions axially spaced from the outward ends; and crossbars joiningthe first and second end rims such that roller receiving slots areformed therebetween, the crossbars having laterally outward portions anda central portion radially offset with respect to the laterally outwardportions; the crossbars being configured such that a roller within oneof the roller receiving slots is retained in the radial directions byengagement with the central portion and with the laterally outwardportions; the periodic depressions being located between the crossbars,one at each end of the roller receiving slots, such that a roller withinone of the roller receiving slots is retained in the axial directions byengagement with the periodic depressions at each end of the rollerreceiving slot.
 2. The roller bearing cage according to claim 1, whereinthe end rims and crossbars are formed from a single sheet of metal andhave substantially the same thickness.
 3. The roller bearing cageaccording to claim 1, wherein the periodic depressions include surfaceshaving an angled profile in longitudinal section.
 4. The roller bearingcage according to claim 1, wherein the periodic depressions includeroller engaging abutment surfaces having a curved profile in transversesection.
 5. The roller bearing cage according to claim 1, wherein thecentral portion and the periodic depressions are both offset radiallyinwardly with respect to the side portions.
 6. The roller bearing cageaccording to claim 1, wherein the central portion and the periodicdepressions are both offset radially outwardly with respect to the sideportions.
 7. The roller bearing cage according to claim 1, wherein thelaterally outward portions of the crossbars include at least one tabextending circumferentially into the roller receiving slots.
 8. Theroller bearing cage according to claim 1, wherein each end rim includesa radially extending flange portion at the axially outward ends of theaxially extending side portions of the end rims.